Interobserver variability in the delineation of the primary lung cancer and lymph nodes on different four-dimensional computed tomography reconstructions

Mercieca, Susan; Belderbos, J.; Jaeger, Katrien De; Schinagl, Dominic A.X.; Zijp, Noëlle van der Voort van; Pomp, J.; Theuws, Jacqueline; Khalifa, J.; Vaart, Paul van de; Herk, Marcel van

doi:10.1016/j.radonc.2017.11.020

Cited by 18 publications

(18 citation statements)

References 21 publications

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“…The GTV and IGTV sizes for the patient cohort shown in 3.1 were similar to [7] [8], mean GTVT and GTVN volumes were smaller on average than mean IGTVT and IGTVN volumes. This difference between GTVT and IGTVT volumes is consistent with previous studies [22]. GTV volume should be close to the tumor volume obtained from a single breathing phase while the IGTV volume encompassed all the tumor positions during the patient breathing.…”

Section: Gtv Volumessupporting

confidence: 91%

Mid-position treatment strategy for locally advanced lung cancer: a dosimetric study

Ayadi

Baudier

Bouilhol

et al. 2020

The British Journal of Radiology

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Objective: The internal target volume (ITV) strategy generates larger planning target volumes (PTVs) in locally advanced non-small cell lung cancer (LA-NSCLC) than the Mid-position (Mid-p) strategy. We investigated the benefit of the Mid-p strategy regarding PTV reduction and dose to the organs at risk (OARs). Methods: 44 patients with LA-NSCLC were included in a randomized clinical study to compare ITV and Mid-p strategies. GTV were delineated by a physician on maximum intensity projection images and on Mid-p images from four-dimensional CTs. CTVs were obtained by adding 6 mm uniform margin for microscopic extension. CTV to PTV margins were calculated using the van Herk's recipe for setup and delineation errors. For the Mid-p strategy, the mean target motion amplitude was added as a random error. For both strategies, three-dimensional conformal plans delivering 60–66 Gy to PTV were performed. PTVs, dose–volume parameters for OARs (lung, esophagus, heart, spinal cord) were reported and compared. Results: With the Mid-p strategy, the median of volume reduction was 23.5 cm3 (p = 0.012) and 8.8 cm3 (p = 0.0083) for PTVT and PTVN respectively; the median mean lung dose reduction was 0.51 Gy (p = 0.0057). For 37.1% of the patients, delineation errors led to smaller PTV with the ITV strategy than with the Mid-p strategy. Conclusion: PTV and mean lung dose were significantly reduced using the Mid-p strategy. Delineation uncertainty can unfavorably impact the advantage. Advances in knowledge: To the best of our knowledge, this is the first dosimetric comparison study between ITV and Mid-p strategies for LA-NSCLC.

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Section: Gtv Volumessupporting

confidence: 91%

Mid-position treatment strategy for locally advanced lung cancer: a dosimetric study

Ayadi

Baudier

Bouilhol

et al. 2020

The British Journal of Radiology

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“…However, these uncertainties will be less than the inter-observer variability for delineations. 41 Major anatomical changes (e.g., GTV shrinkage) also make it difficult to propagate GTV contours using deformable image registration algorithms alone. A thorough checking with manual adjustments was performed in this study, to cope with this issue.…”

Section: Discussionmentioning

confidence: 99%

Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

et al. 2020

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For locally advanced-stage non-small cell lung cancer (NSCLC), inter-fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS-PT) treatments of NSCLC patients during free breathing. Methods: Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases. Results: The median observed centroid motion was 3.4 mm (range: 0.2-12.4 mm) with an average variation of 2.2 mm (range: 0.1-8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5-mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0-6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case. Conclusions: Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed.

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“…Given these advantages, the question arises as to why there has not been widespread adoption of the mid-V or mid-P methods, and that the ITV method remains the one most commonly used clinically [5]. One possible reason is a perception that the method does not provide adequate coverage.…”

Section: Discussionmentioning

confidence: 99%

“…A recent study of clinical practice found that the majority of radiotherapy centres use the ITV method, with only 6% of centres using the Mid-V or Mid-P method [5]. There are two main reasons for the slow uptake of the Mid-V or Mid-P approach.…”

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confidence: 99%

An evaluation of the mid-ventilation method for the planning of stereotactic lung plans

Thomas

Evans

Harihar

et al. 2019

Radiotherapy and Oncology

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a b s t r a c tBackground and purpose: Stereotactic ablative body radiotherapy for lung plans requires 4DCT. Most radiotherapy centres use this to determine an internal target volume (ITV), despite studies suggesting that planning on a mid-ventilation (Mid-V) phase can reduce target volumes. The purpose of this study is two-fold: to determine whether the Mid-V approach provides adequate coverage and to discuss methods to enable the Mid-V approach to be applied more widely. Method: 4D scans of 79 patients were outlined on every phase. The mid-V phase was identified. Margins were determined from the range of motion, and plans generated with a 55 Gy prescription. A grid-based method was used to get the probability of tumour coverage in the presence of systematic and random uncertainties, with and without blurring for breathing motion. Results: For the Mid-V plans with the margins calculated from the van-Herk formula, after blurring doses for breathing, the coverage (dose covering 95% of the CTV 95% of the time) was greater than for plans with isotropic 5 mm margins uncorrected for breathing (58.2 Gy v 57.3 Gy). Similar results were obtained for a linear margin chosen as 0.15 of the breathing range. Deformable contour propagation in a commercial outlining system (ProSoma) identified the same mid-V phase in the majority of cases. Conclusion: Our results confirm that a mid-V approach can be used to reduce the PTV size, with no loss of tumour coverage. We propose the use of a simplified margin formula equal to the margin ignoring breathing plus 0.15 of the range of motion.

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Interobserver variability in the delineation of the primary lung cancer and lymph nodes on different four-dimensional computed tomography reconstructions

Abstract: The Mid-P reduced the interobserver variation for the GTVp. Delineation protocols must be improved to benefit from the improved image quality of Mid-P for the GTVln.

Cited by 18 publications

References 21 publications

Mid-position treatment strategy for locally advanced lung cancer: a dosimetric study

Mid-position treatment strategy for locally advanced lung cancer: a dosimetric study

Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

An evaluation of the mid-ventilation method for the planning of stereotactic lung plans

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